Data analysis for spectroscopic ellipsometry

The modeling of spectroscopic ellipsometry data is reviewed, and is divided into three phases. The first phase involves the calculation of the Fresnel reflection coefficients for a given layer structure; it is shown that the Abelès formalism provides the most flexibility, and can be readily related to the Berreman formalism for calculations involving anisotropic layers. The second phase is to parameterize the optical functions of each individual layer; several models are reviewed, including effective media, the Lorentz oscillator and a recent parameterization of amorphous semiconductors. The final phase involves the fitting of the spectroscopic ellipsometry data to the model, where different figures of merit of the fitting function are discussed. A proper numerical analysis technique requires that the reduced ¢2 be used as the figure of merit, which will result in the proper weighting of data points, and in obtaining meaningful error limits and a measure of the goodness of fit.